The present invention relates to a method for regenerating used halide fluids. More specifically the invention relates to enhancing used halide fluids by removing impurities, increasing the density of the halide fluid, and increasing the concentration of electrolytes and adjusting the true crystallization temperature of the fluid.
Clear brine fluids used in deep oil and gas wells or other industrial and agricultural processes become diluted due to the increased concentration of water in the system. In addition, these fluids can become contaminated with impurities such as metallic cations, hydrocarbons and organic polymers. At some point, the overall quality of the brine, density and true crystallization temperature (TCT) in particular, changes to a level that does not conform to product specifications.
Brine fluids are expensive to produce. Due to the high amounts of chlorides, bromides and, in some brines, zinc that are present in the used fluids, the disposal of used clear brine fluids is also very costly. It is highly desirable that a used halide fluid be recuperated, regenerated and recycled back into operation.
The current industrial practice for the treatment of recuperated used brines from oil and gas wells involves introduction of additional electrolyte of the fluid composition to adjust the density and the resulting TCT of the brine to the desired level. The process of adding liquid electrolyte to the used brine necessarily introduces even more water into the system. Dissolving a solid electrolyte, calcium chloride for example, is a slow and tedious process that may also require the addition of more water to the brine. Solid electrolytes are also very costly thereby making this method expensive. Another significant disadvantage of the currently utilized method in the industry is that some electrolytes are pH sensitive and can be easily lost due to precipitation. For example, the zinc ions from a brine containing zinc bromide or zinc chloride will start precipitating as zinc hydroxide at a slightly acidic or alkaline pH. As a result, the density of the solution that is being regenerated will drop substantially. The change in the density also changes the TCT of the fluid, so that the fluid is unable to meet the specification set by the needs of the oil field for TCT value of the fluid. Using the methods of evaporation or blending to increase density or to adjust the TCT is time consuming, expensive and difficult to control.
Oliver et al., U.S. Pat. No. 4,592,425, discloses a process for removal of small amounts of settled solids, i.e. drilling residue, mud, solids and oil, from the brine at the production zone of interest without reprocessing the entire volume of brine within the well bore. The settled solids are spotted (treated) in a mixture of an aliphatic alcohol with between 5 and 14 carbon atoms and a surfactant with a molecular weight in a range from about 150 to 500 with predominantly hydrophobic characteristics. The surfactant is selected from the group consisting of aliphatic amines, amides and aliphatic amine oxides with an alkyl group between 8 and 18 carbon atoms. The amount of both the alcohol and the surfactant must be empirically determined for each application. Upon spotting in the solids with the aliphatic alcohol-surfactant mixture, the solids become buoyant in the brine and rise to the to the top of the well bore thus leaving the well production zone with clean, solids-free brine.
Gilligan III, U.S. Pat. No. 4,548,720, discloses a process for scavenging hydrogen sulfide from drilling fluids by adding solid oxidants, such as potassium permanganate, sodium perforate, potassium peroxidisulfate and calcium hypochlorate. These oxidants dissolve in the drilling fluid and convert hydrogen sulfide into free sulfur and innocuous sulfur by-products.
Luxemburg, U.S. Pat. No. 4,451,377, discloses a process for cleaning oil-contaminated well bore fluids containing particulate drill cutting solids by admixing the fluid with an aqueous polymeric solution and diatomaceous earth, and then filtering the admixture. Kadija et al., U.S. Pat. No. 4,207,152, discloses a process for removing cationic contaminants from alkali metal chloride brines used in electrolytic processes such as the production of chlorine and alkali metal hydroxides or alkali metal chlorates. The alkali metal chloride brine is treated with solid particles of magnesium-containing silicate.
What is needed is a method that allows for an efficient regeneration of the recuperated used brine fluid in a controlled manner. A method that removes metallic cationic impurities and avoids both precipitation and conditions that increase dilution and adversely affect the TCT of the fluid by addition of water into the recuperated brine fluid is also desirable.
The present invention relates to an innovative method for regeneration of used halide fluids that have been recuperated from industrial processes such as oil and gas drilling, agricultural chemical processes, metal plating or water treatment. Used halide fluids, bromide or chloride brines for example, are usually contaminated with soluble and insoluble impurities. For example, during well operation procedures, because of the continuous contact with water, these recuperated, used fluids typically have a density greater than 9.0 lbs/gal but less than the required density of a desired drilling fluid. To remove impurities, increase the density, adjust the resulting TCT and enhance the concentration of electrolytes, one preferred method of regeneration of a used halide fluid comprising soluble and insoluble impurities and having a density greater than 9.0 lbs/gal comprises adding an acid to the used halide fluid. The used halide fluid is then contacted with a halogen, bromine for example, to increase fluid density and oxidize impurities. Alternatively, a halogen-generating species, such as oxyhalogen salts, hypochloride, hypobromide and the like can be used to increase density, adjust TCT and oxidize impurities. The used halide fluid, if comprising a high solid content, should be filtered to remove the solids prior to acidification.
A reducing agent can be added to convert halogen to halide ion while maintaining the temperature at a minimum of 10xc2x0 C. Preferably, the fluid is then contacted with an alkali to neutralize any excess acid. Any suspended solid impurities remaining can be separated from the fluid. During the method, it is preferred that if the metallic cations are from a base metal group, the pH can be maintained within a range of approximately 0.0 to 5.5. For the alkali and alkali earth metal cations this range can be from 0.0 to 10.0. The acid used for acidification can comprise hydrobromic acid. Alternatively the acid can comprise hydrochloric acid or an organic acid. The reducing agent is preferably selected from a group consisting of ammonia, sulfur, hydrogen sulfide, sodium bisulfide, metallic zinc, metallic iron, metallic copper, metallic nickel, metallic cadmium, metallic cobalt, metallic aluminum, metallic chromium, metallic manganese, organic acids, alcohols and aldehydes.
In one aspect, the electrolyte to be enhanced in the used fluid is salt of alkali metal, an alkali earth metal or a base metal. If the alkali earth metal is calcium, the alkali used to neutralize excess acid can be calcium hydroxide or calcium oxide. Alternatively, if the alkali earth metal in the used fluid is strontium, the alkali used to neutralize excess acid is preferably strontium hydroxide or strontium oxide.
In another preferred method, the alkali used to neutralize excess acid is an alkali metal hydroxide, sodium hydroxide or potassium hydroxide for example. Ammonia can also be used to neutralize excess acid.
In another preferred method the alkali used to neutralize excess acid is a base metal hydroxide or base metal oxide, such as zinc hydroxide, zinc oxide, copper hydroxide or copper oxide.
In another preferred method, the alkali used to neutralize excess acid is aluminum hydroxide or aluminum oxide, manganese hydroxide or manganese oxide, chromium hydroxide or chromium oxide.
One embodiment of the method for regeneration of used halide fluids comprising soluble and insoluble impurities comprises the steps of:
a) determining density of the used halide fluid;
b) analyzing chemical composition, the suspended solids content and the oil and grease content of the used halide fluid;
c) separating the suspended solids and oil and grease from the used halide fluid;
d) adding acid to the used halide fluid;
e) contacting the used halide fluid with halogen or halogen-generating species to increase fluid density and oxidize impurities;
f) adding a reducing agent while maintaining the temperature at a minimum of 10xc2x0 C.;
g) contacting the fluid with an alkali to neutralize excess acid;
h) separating any suspended solid impurities from the fluid.
In one preferred embodiment, the recuperated used halide fluid is piped into a reactor after density and chemical composition have been determined according to steps (a) and (b). In one aspect of the practice of this invention, the acid, halogen, reducing agent and alkali can be piped into reactor along with the fluid. Alternatively, the acid, halogen, reducing agent and alkali can be transported separately to the reactor. Bromine is one preferred halogen used in regeneration.
Another preferred method regenerates a used halide fluid comprising a blend of a group of halide salts, such as calcium chloride, calcium bromide, zinc bromide or a combination thereof. The starting brine fluid will typically have a density greater than 9.0 lbs/gal. and contain both soluble and insoluble impurities. This method comprises the steps of (1) adding acid to the used halide fluid so that the pH is within a range of approximately 0.0 to 5.5 for a base metal or 0 to 10.0 for alkali and alkali earth metal systems; (2) contacting the used halide fluid with bromine to increase the density to at least 10.0 lbs./gal. and oxidize soluble impurities; (3) adding a reducing agent while maintaining the temperature at a minimum of 10xc2x0 C.; (4) contacting the fluid with an alkali to neutralize excess acid; and (5) separating any suspended solid impurities from the fluid.